The Audio-Powered Baby Mobile (APBM) is an entertainment system that operates based on the input from a crying child and can be controlled by a parent. Once the APBM is turned on, two green LEDs signal that a microphone sensor is measuring sound levels in a room because the power source is on. If a child cries in the vicinity of the APBM, the microphone on the breadboard detects a difference in the frequency of noise in the room, triggering two main outputs. The DC motor output will spin heart-shaped stimuli at the base of the APBM frame. At the same time, a servo motor output will also continuously rotate a tongue depressor from the top of the APBM’s wooden frame, causing the attached stimuli to rotate. The rotation of this top tongue depressor and its attached paper objects creates a soothing, spinning mobile effect that children can view from any angle. The APBM breadboard also has a button sensor that allows the parent to temporarily stop the motor for safety if a child gets too close, by pressing down for just a few seconds. The overall mechanical structure of the APBM consists of two bisecting rectangular tongue depressor frames with hanging paper objects, which will support the motor and servo elements. This is a prototype version of what an actual APBM would look like.

Supplies

Main Bill of the Materials for this Project

(See BOM image in STEP 7 for exact sources of Materials)

1 MAX4466 Microphone Pre-Amp Audio Evaluation Board (Sensor)

10 Tounge Depressors

2 pieces of 8.5" x 11" 22Pt Cardstock (Green & Orange)

1 Plastic Pencil Box Embroidery

1 String

1 Bottle Modge Podge glue

1 Green Masking Tape Roll

2 100 Ohm Resistor, 5%, 1/4 W

1 Axial Tactile Switch Push Button

2 Green LEDs

4-AA Battery Holder

4 AA Batteries

1 USB Cable A to B

1 Alligator Clip Lead Wire Kit

1 Arduino Board Bread Board

1 Micro Servo continuous rotation

1 Mini DC motor 1.5-12VDC 1350 Rpm

1 Motor Driver IC: L9110H

1 Mini Breadboard

1 Small Screwdriver

1 USB Cable A to MicroB

Step 1: Build Your Circuit

Follow the circuit diagram from above, and use your breadboard to fully craft your circuit. A reference image of the circuit is also provided to illustrate on model for circuitry. Feel free to add more sensors or LEDS!

Step 2: Build Your Frame + Add Your Motor/Servo

You can follow the exact images in the images above or in the Assembly PDF below!

Basic Frame

Tap two small holes in the middle of two tongue depressors using a small screwdriver, and then glue them in an x formation so that the holes overlap (See Figure 1 & 2a/b in Appendix C). The angle of x formation is not consequential.

Cut the ends off of two tongue depressors, and proceed to cut the rectangular sections in half. You should have four rectangular pieces now (See Figure 3 in Appendix C for Dimensions of Pieces in mm).

Glue each of the rectangular pieces onto one of the four corners of the original tongue depressor cross from step.

Reinforce glue joints with cardstock and leftover scraps from tongue depressors (Figure 4 in Appendix C).

Create another tongue depressor cross just like in step one and glue the four corners of the cross to the upright rectangular pieces.

Your final product should look like Figure 5 in Appendix C.

Decorations + Servo Placement

Cut six paper hearts (roughly 4 cm x 4 cm dimensions) out of the cardstock, then punch holes in the corner of four of them. Cut four pieces of string, and tie the strings to four of the hearts. Then tie two of the attached two string-heart suspensions to the ends of one of the top-most tongue depressors (See Figures 6a/b in Appendix C). Obtain a new tongue depressor and tap a hole into the top just like in step one. From there, use a servo screw (provided with servo) to attach the tongue depressor to a servo with a screw. Then proceed to tie the remaining two string-heart suspensions to the ends of this new tongue depressor. (See Figure 7 in Appendix C) Attach the servo and its tongue depressor to the top of the main APBM wooden frame with a piece of inside-out tape. (See Figure 8 in Appendix C for Placement).

Motor Placement

Then slide a small piece of inside-out tape over the motor’s driveshaft (with the non-sticky side touching the shaft so that no damage is done). Then place the two remaining hearts on either side of the piece of tape. (See Figure 9 in Appendix C for this). Place the motor’s untouched, shorter shaft end into the bottom hole of the wooden frame. The motor should rest evenly on the tongue depressor. (See Figure 9 & 10 in Appendix C).

Final Report Mechatronics.pdf
Download

Step 3: Elevate Your Mobile

Place the whole Wooden Assembly on top of a cheap pencil box for height and stability! You can also make a hole in your pencil box to support the motor shaft, it it is too long. Feel free to add more stimuli or hearts on your mobile.

Step 4: Operation Instructions

Once the device is fully assembled, connect the computer and Arduino using USB Cable A to B After verifying and uploading the code, open the serial monitor within Arduino IDE and turn on the 6V battery pack. Two LEDs should light up, indicating the power source is connected to the board. The serial monitor display should also show numbers less than 4, indicating it is quiet. Make a baby noise or create a high-pitched noise, and the DC motor and servo motor will automatically start spinning on the device. The serial monitor will display values greater than 4, to indicate sound is being detected and the motor and servo should be operational. To stop the motor temporarily, press the button sensor on the board. The motor will resume spinning shortly after stopping, as the sound is detected. If you wish to turn off the operations entirely, turn off the battery pack and unplug the computer-Arduino connection.

Step 5: CAD Files

The attached CAD files give in-depth dimensions for the parts used, and the overall placement of parts.

Step 6: Code

The following Arduino code controls the functions of all sensors, motors, and servos. It can be directly downloaded and modified. Make sure you check the pins, if your circuit contains differences.